A couple of cheerleaders put dog shit into brownies and gave them to a teacher, because the teacher wouldn't let them wear their cheerleading uniform in class.
Also, I'm not sure when, but a long time ago a science teacher had a chemical that, when in contact with water, exploded. A dumbass student went in and got the chemical sample and thought it would be fun to play with at home. He was planning to throw it into a lake near his home, but during lunch some tea spilled onto him. His leg was blown off. I wasn't at the school at the time, but hory sheet.